Questions and answers on LED bulbs

Who knew that LEDs would be the hottest topic in real estate? Judging by my reader mail, it’s on many homeowners’ minds, now that the manufacture of 40-, 60-, 75- and 100-watt incandescent bulbs has been phased out, a process that began in 2012 and ended on Jan. 1.

To help homeowners navigate this momentous change in home lighting, I wrote a cover story for the Real Estate section in late December about the LED equivalent of the 60-watt incandescent, the most widely used of the phased-out bulbs. Reader mail poured in. Here are some of the questions I received and my responses. I'll answer more questions, including which brands I preferred in my home testing, Monday in my blog at washingtonpost.com/wherewelive.

Can an A19 LED (the bulb designed to replace Edison’s iconic incandescent bulb) be used with the type of lampshade that clamps directly to the bulb?

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Yes. A clamp type of lampshade will not damage the bulb; the only issue is whether the shade will clamp over the bulb. The shape of some A19 LEDs differs quite a bit from the old-style incandescent, but all the ones I tested worked with a clamp lampshade, including Philips’s SlimStyle, which is shaped like a mini ping-pong paddle.

Do A19 LEDs work with dimmers?

Yes, if the package says “dimmable.” But the A19 LED bulb may not be compatible with the dimmers in your house, especially if they are more than 10 years old. Recognizing that this is an issue, both the dimmer manufacturers and the LED bulb manufacturers have worked hard to make their products compatible with each other.

How can I find out if an A19 LED will work with the dimmer in my house?

You can contact the manufacturer of the dimmer. (If the name is not visible on the faceplate with the light switch, you may have to remove it and look inside the switch box that is recessed into the wall.) Most A19 LED manufacturers list compatible dimmers on their Web sites.

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Alternatively, you can buy an A19 LED bulb and test it with your dimmer. You won’t cook the bulb if the dimmer is incompatible; you just won’t like the results. The symptoms of a mismatch are audial — a buzzing noise that increases with dimming — and/or a flickering, strobe-light effect.

If your dimmers are compatible, you will still notice two significant differences compared with their performance with an incandescent bulb. The first is the amount of light that is still visible when the dimmer is turned all the way down. Because the LED is so much more efficient, the slightest amount of current will illuminate the bulb, but some dimmers can be adjusted so that no current passes through when the dimmer is turned all the way down.

The second difference is the appearance of the dimmed light. As an incandescent bulb is dimmed, both the amount of light and the color temperature are reduced. The light becomes more reddish, which enhances your perception that it is becoming more faint. When an A19 LED is dimmed, only the amount of light is reduced; the color temperature of the light remains the same.

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As a consequence, when the LED is dimmed 70 percent, it will appear to be brighter than an incandescent dimmed an identical amount.

Is there a three-way LED bulb?

Readers who asked about this were especially interested in a three-way LED bulb that goes up to 150 watts (50/100/150) because they need the brighter light for reading. The good news here is that the three-way incandescent bulb is classified as “nonstandard” and it’s still being manufactured. Also Ecosmart (Home Depot’s house brand $20) offers a three-way A19 LED that’s a 25/40/60-watt equivalent.

Can an LED be used in an enclosed fixture?

Yes, but only some brands. The issue is the amount of heat that can build up in the enclosed fixture. LED bulbs are very sensitive to heat; if the air in the enclosed fixture becomes too hot, it will shorten the life of the bulb.

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If you want to install an A19 LED 60-watt equivalent in an enclosed ceiling fixture (the most common type of residential enclosed fixture), read the packaging carefully. Most say that the bulb cannot be used in this way. The only ones I found that can be are Cree’s A19 LED Soft White and its A19 Soft White TW Series. The fine print on Cree’s packaging, however, warns against mixing bulb technologies in the fixture (using a LED with a CFL or an incandescent) because the other bulb types produce so much heat that they will adversely affect the LED.

Katherine Salant has an architecture degree from Harvard. A native Washingtonian, she grew up in Fairfax County and now lives in Ann Arbor, Mich. If you have questions or column ideas, she can be contacted at salanthousewatch@gmail.com or katherinesalant.com .

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